Ambike Satyajit, Mattos Daniela, Zatsiorsky Vladimir M, Latash Mark L
Department of Health and Kinesiology, Purdue University, Lambert Fieldhouse, Room 110B, 800 West Stadium Avenue, West Lafayette, IN, 47907, USA.
Department of Kinesiology, The Pennsylvania State University, University Park, PA, USA.
Exp Brain Res. 2016 Jan;234(1):197-208. doi: 10.1007/s00221-015-4453-z. Epub 2015 Sep 29.
We explored unintentional changes in forces during performance of constant and cyclic force-production tasks (F-tasks) after visual feedback removal. Based on earlier studies, we expected all force parameters to drop exponentially with time. We also explored possible role of working memory in the force drop phenomena. Healthy subjects performed constant or cyclic isometric F-tasks with the index finger under visual feedback. The cyclic task was paced by a metronome. Removing visual feedback resulted in a consistent force drop in constant F-tasks and a qualitatively similar drift in the mean force in the cyclic F-task. Both were slow with characteristic times of about 10-20 s. In contrast, force amplitude in the cyclic F-task increased quickly (within 1-2 s). When the subjects were asked to stop producing force for 5 s after the visual feedback disappeared and then resume force production, no downward force drift was seen in constant F-tasks, while in cyclic F-tasks, the drift of the mean force was present and an exaggerated increase in force amplitude was also observed. We conclude that while working memory limitations may influence cyclic F-tasks, their role in determining the force drift in constant F-tasks is limited. The results of both experiments are interpreted within the referent configuration hypothesis supplemented with an idea of unintentional drift of referent coordinates (RC-back-coupling) induced by differences between the referent and actual body configurations.
我们探究了在去除视觉反馈后，执行恒定和循环力产生任务（F任务）期间力的无意变化。基于早期研究，我们预期所有力参数会随时间呈指数下降。我们还探究了工作记忆在力下降现象中可能扮演的角色。健康受试者在视觉反馈下用食指执行恒定或循环等长F任务。循环任务由节拍器控制节奏。去除视觉反馈导致恒定F任务中力持续下降，以及循环F任务中平均力出现性质相似的漂移。两者下降速度都很慢，特征时间约为10 - 20秒。相比之下，循环F任务中的力幅快速增加（在1 - 2秒内）。当要求受试者在视觉反馈消失后停止用力5秒，然后恢复用力时，恒定F任务中未观察到向下的力漂移，而在循环F任务中，平均力的漂移存在，并且还观察到力幅的夸张增加。我们得出结论，虽然工作记忆限制可能影响循环F任务，但它们在决定恒定F任务中的力漂移方面作用有限。两个实验的结果都在参考构型假说的框架内进行解释，该假说补充了由参考构型与实际身体构型之间的差异引起的参考坐标无意漂移（RC回耦）的概念。
